Incineration



W. RAISCH July 119, 1938.

INC INERATION Filed Nov; 7, 1956 C H mm N M m E W W A M Patented July 19, 1938 UNITED TA'ES PATET l FEQE INCINERATION Application November 7, 1936, Serial No. 109,616

7 Claims.

The present invention relates to incineration and more particularly to improvements in processes of incineration and in multiple-hearth furnaces in which the material to be treated is fed downwardly from hearth to hearth and at one hearth the flow of air and gases along the path followed by the solid material is prevented, thus dividing the furnace into two sections, one of which may be used only for drying and the other only for burning thus enabling better control of temperatures and flow of. gases through the two sections.

The principal objects of the invention are to provide novel, advantageous and efficient forms of apparatus and processes for effecting treatment of the general character specified. Another object is to provide improved means for heating in the furnace itself air and gases passing from the drying section to the burning section. A further object is to provide, in a furnace comprising an upper drying section and a lower burning section, means for conducting air and vapor from the drying section to the burning section in heat exchange relation to the hot gases in the burning section before discharging the air and gases into the burning section,

In carrying out the invention in a preferred manner, use may be made of a multiple-hearth furnace separated into an upper or drying section and a lower or burning section by a hearth having one or more outlets for discharge of solids to the next lower hearth, and a gas seal for each outlet. By use of such gas seals, it is made possible to control to better advantage the flow of air and gases through the drying and burning sections. Air preferably preheated is supplied to the upper part of the drying section and withdrawn from the lower part of this section into downwardly extending ducts at the inner surface of the peripheral wall and discharging into the lower part of the burning section through which the draft is upward to an outlet or discharge opening in the upper part of the burning section. The ducts may be made of material adapted for heat interchange between hot gases in the burning section and the air and vapors passing through the ducts to the lower part of the burning section. The hot gases from the burning section may be used to preheat air supplied to the drying section.

Other objects, features and advantages will appear upon consideration of the following description of the drawing, in which:

Fig. l is a View in vertical section of an improved embodiment of the invention; and

Fig. 2 is a section on the line 22 of Fig. 1.

Referring to the drawing, the invention may be embodied in a furnace It provided with a top H and hearths l2, I3, 54, l5, l6 and H, of which the hearth l'l serves as a bottom of the furnace or furnace chamber.

The material to be treated may be introduced into the furnace and deposited upon the uppermost hearth l2 through a hopper l8 and a chute I 9 extending through the top H of the furnace and provided with a pivoted door or gate 2t normally held closed by suitable means such as a weighted arm 25. As soon as a sufficient amount of material to overcome the action of the weighted arm 2! collects on the door or gate 20, the door swings downwardly about its pivotal support and permits the material on the door to fall to the hearth l2.

As illustrated, this material falls on the hearth l2 near its periphery and is worked inwardly to a central discharge opening 22 by suitable rabbling means including one or more radial arms 23 and inclined blades 24 carried thereby. Below the hearth E2, the hearths I? and 15 are provided with peripheral outlets 25, the hearths I l and it are provided with central outlets 22 corresponding with the central outlet of the hearth l2, and the lower hearth ii is provided with a single outlet or chute 26 through which the ash is discharged from the furnace. The chute 26 is preferably provided with a gas seal in the form of a pivoted door 21 normally held in closed position by a weighted arm 28.

The material on the hearths it, Hi, l5, I6 and H is moved towards the corresponding outlets by suitable rabbling means similar to that used above the hearth l2, the blades 28 above the hearths l3, I5 and H being so inclined as to carry the material outwardly to the peripheral outlets thereof, and the blades above the hearths I l and It being so inclined as to work the material toward the central opening as in the case of hearth [2.

The rabbling arms 23 may be supported and operated by a hollow vertical shaft 29 passing through the central parts of the central outlets 22 of the hearths l2, l4 and i6 and through small openings in the top I l and the hearths I3, l5 and I1, suitable gas seals being provided where the shaft 29 passes through the top and these hearths. The shaft 29 may be rotated in any suitable manner as by means of a bevel gear 30 thereon, a bevel gear 3i meshing with the bevel gear 33, and a pulley 32 connected with the bevel gear 3| and driven from any suitable source of power.

The hearth l3 may be used to divide the furnace into an upper drying section and a lower burning section. Although this hearth may have more than one outlet 25, it may be desirable to have only one outlet to render it more easy to effect gas sealing at this hearth. As illustrated, use is made of a sweep valve 33 including a tube 34 in the outlet 25 and extending downwardly to a level slightly above a fixed shelf 35 on which the material piles up and normally closes the lower end of the tube 34, and one or more sweep members 36 carried by rabble arms 23 in the compartment below the hearth l3. It will be evident that each time a sweep 36 removes some material from a shelf 35, the material in the corresponding tube or chute 34 settles without breaking the gas seal.

In the drying and burning operation, air, preferably preheated, is supplied to the drying section and after acting on the material therein is passed, together with vapors taken up in the drying section, into the burning section where it aids combustion. All noxious odors are eliminated and the hot combustion gases are discharged from the furnace. Air may be supplied to the drying section by means of a fan 3'! and a duct 33 leading to the uppermost compartment of the drying section. The air thus supplied may be preheated by passing it through a heat exchanger 39.

The preheated air is reduced in temperature and takes up vapors of moisture and volatile material in passing through the drying section and it is therefore desirable to supply more heat thereto before it is discharged into the burning section. Preferably this is done by means of ducts or pipes 40 partially embedded in the peripheral wall of the furnace at its inner surface. The ducts or pipes 40 may be made of high heat resisting material and may be provided at their upper ends with lateral inlets 4| communicating with the interior of the lower compartment of the drying section, and with lateral outlets 42 communicating with the lowermost compartment of the burning section. The upper and lower ends of the pipes 40 may be in engagement with or embedded in the hearths l2 and I1 respectively. It is desirable to provide burners 43 for use in starting the apparatus or in raising the temperature where required, and also to provide doors 44 for inspection and other purposes. Where burners or doors are placed, pipes 40 must be omitted.

The hot gases from the burning zone are passed through a duct 45 to the heat exchanger 39 and then through a fan 46 to the stack 41.

It will be understood that the furnace may have any desired number of hearths in the furnace and in the drying and burning sections.

While applicable to the treatment of various materials, the present invention is particularly adapted for the disposal and destruction of waste materials, such as garbage and sewage solids in the form of sludge or in the form of screenings having high moisture content.

It should be understood that various changes may be made and that certain features may be used without others without departing from the true spirit and scope of the invention.

Having thus described my invention, I claim:

1. In apparatus of the class described, the combination with a multiple-hearth furnace having a peripheral wall, vertically spaced hearths with outlets through which material introduced at the top of the furnace is passed from hearth to hearth to the lowermost hearth and then discharged from the furnace, means at the outlet of one hearth for preventing the passage of gases and dividing the furnace into an upper drying section and a lower burning section, means for supplying air to the drying section and means for discharging hot combustion gases from the higher part of the burning section, of means for conducting air and vapor from the drying section downwardly in heat-exchanging relationship with the combustion gases in the burning section, and discharging the air thus heated into the lower part of said burning section.

2. In apparatus of the class described, the combination with a multiple-hearth furnace having a peripheral wall, vertically spaced hearths with outlets through which material introduced at the top of the furnace is passed from hearth to hearth to the lowermost hearth and then discharged from the furnace, means at the outlet of one hearth for preventing passage of gases and dividing the furnace into an upper drying section and a lower burning section, means for supplying air to the drying section and means for discharging hot combustion gases from the higher part of the burning section, of means including downwardly extending ducts at the inner surface of said peripheral wall for conducting air and vapor from the drying section downwardly in heat exchanging relationship with the combustion gases in the burning section, and discharging the air thus heated into the lower part of said burning section.

3. In apparatus of the class described, the combination with a multiple-hearth furnace having a peripheral wall, vertically spaced hearths dividing the furnace into compartments and provided with outlets through which material introduced at the top of the furnace may pass from hearth to hearth to the lowermost hearth and then be discharged from the furnace, means at the outlet of one hearth for preventing the passage of gases and dividing the furnace into an upper drying section and a lower burning section, means for supplying air to the drying section and means for discharging hot combustion gases from the higher part of the burning section, of means for conducting air and vapor from the drying section downwardly in heat-exchanging relationship with the combustion gases in the burning section, and discharging the air thus heated into a lower part of said burning section, such air-conducting means including ducts with lateral outlets arranged at the inner surface of the peripheral wall and embedded at their lower ends in a hearth below the compartment into which the air and vapors are discharged.

4. In apparatus of the class described, the combination with a multiple-hearth furnace having a peripheral wall, vertically spaced hearths dividing the furnace into compartments and provided with outlets through which material introduced at the top of the furnace may pass from hearth to hearth to the lowermost hearth and then be discharged from the furnace, means at the outlet of one hearth for preventing the passage of gases and dividing the furnace into an upper drying section and a lower burning section, means for supplying air to the drying section and means for discharging hot combustion gases from the higher part of the burning section, of means for conducting air and vapor from the drying section downwardly in heat-exchanging relationship with the combustion gases in the burning section, and discharging the air thus heated into the lower part of said burning section, such airconducting means including ducts with lateral inlets arranged at the inner surface of the peripheral wall and embedded at their upper ends in a hearth above the compartment from which the air and vapors are received.

5. In apparatus of the class described, the combination with a multiple-hearth furnace having a peripheral wall, vertically spaced hearths dividing the furnace into compartments and provided with outlets through which material introduced at the top of the furnace may pass from hearth to hearth to the lowermost hearth and then be discharged from the furnace, means at the outlet of one hearth for preventing the passage of gases and dividing the furnace into an upper drying section and a lower burning section, means for supplying air to the drying section and means for discharging hot combustion gases from the higher part of the burning section, of means for conducting air and vapors from the drying section downwardly in heat-exchanging relationship with the combustion gases in the burning section, and discharging the air thus heated into the lower part of said burning section, such air conducting means including ducts with lateral inlets and outlets near their ends and arranged at the inner surface of the peripheral wall and embedded at their upper ends in a hearth of the drying section and at their lower ends in a hearth of the burning zone.

6. In apparatus of the class described, the combination with a multiple-hearth furnace having vertically spaced hearths with outlets, through which material introduced at the top of the furnace may pass from hearth to hearth to the lowermost hearth and then be discharged from the furnace, means at the outlet of one hearth for preventing the passage of gases and dividing the furnace into an upper drying section and a lower burning section, means for supplying air to the drying section and means for discharging hot combustion gases from the higher part of the burning section, of means for conducting air and vapor from the drying section downwardly in heat-exchanging relationship with the combustion gases in the burning section and discharging the air thus heated into the lower part of said burning section and means for preheating air for the drying section by means of the hot waste gases from the burning section.

7. In apparatus of the class described, the combination with a multiple-hearth furnace having a peripheral wall, vertically spaced hearths with outlets through which material introduced at the upper part of the furnace is passed downwardly from hearth to hearth and discharged from the lower part of the furnace, means at the outlet of one hearth for preventing the passage of gases and dividing the furnace into an upper drying section and a lower burning section, means for supplying heated gases to the drying section, and means for discharging hot combustion gases from the burning section, of means for conducting gases and vapors from the drying section downwardly at the interior surface of the peripheral wall and in heat-exchanging relationship with the hot combustion gases in the burning section, and discharging the gases and vapors thus heated into the burning section.

WILLIAM RAISCH. 

